Transdermal venous access locking solutions

ABSTRACT

Microbial growth inhibiting solutions and methods of employing the microbial growth inhibiting solutions in flushing and coating medical devices are disclosed. In alternative embodiments, the microbial growth inhibiting solutions include combinations of a chelating agent with a C 4 -C 9 , C 10  or C 12  carboxylate antimicrobial agent, for example, such as n-capric, n-lauric, or n-octanoic acid. Methods of using these microbial growth inhibiting solutions for coating a medical device and for inhibiting catheter infection are also disclosed.

PRIORITY CLAIM

This application is a continuation-in-part of patent application Ser.No. 13/222,221, filed on Aug. 31, 2011, which is a continuation-in-partof patent application Ser. No. 12/383,722, filed on Mar. 26, 2009, theentire disclosures of which are incorporated by reference.

FIELD

This invention relates to the field of transdermal indwelling medicaldevices, such as catheters, as well as to the field of microbial growthinhibiting solutions for flushing, locking and coating these medicaldevices. More specifically, the field of this invention relates tomicrobial growth inhibiting solutions. This invention also relates tomicrobial growth inhibiting solutions useful in maintaining catheterpatency and preventing infection. Methods of using the microbial growthinhibiting solutions of the invention in the management and maintenanceof transdermal vascular access catheters are also related to the presentdisclosure.

BACKGROUND

Transdermal medical devices, including vascular catheters, have becomeessential in the management of hospitalized or chronically ill patients.Unfortunately, vascular catheters have become the major source forhospital-acquired sepsis. Hence, the benefit derived from transdermalmedical devices such as vascular catheters is often upset by infectiouscomplications. Thrombotic occlusions of the lumen of central venouscatheters (“CVC”) are another complication that will often lead to theremoval of catheters.

To reduce problems associated with thrombus formation, it is now commonto “lock” intravascular access catheters between successive uses.Locking typically involves first flushing the catheter with saline toremove blood, medications, cellular debris and other substances from thecatheter lumen. After the catheter has been flushed, a locking solution,typically heparin, is then injected to displace the saline and fill thelumen. The heparin locking solution both excludes blood from the lumenand actively inhibits clotting and thrombus formation within the lumen.To address infection, various antimicrobial substances have beencombined with the locking solution in order to inhibit infection at thesame time that thrombosis is being inhibited. However, problems withcurrent and continuously emerging resistance to antimicrobialsubstances, as well as the over-use (and hence the increased risk ofdeveloping resistance) of antimicrobials, is an ever-growing concern.

Staphylococcus epidermidis and S. aureus account for 75% of CVC relatedinfections. Candida species account for another 10% to 15% of suchinfections. The use of antistaphylococcal antibiotics to prevent theseinfections has been found to reduce CVC related bacterial infections,but only at the expense of the occurrence of higher rates of fungal(Candida) infections. The fibrous glycocalyx material produced byStaphylococci and Candida helps these organisms adhere and stick tocatheter surfaces. These microbiological biofilm layers are made offibrous glycocalyx material primarily polysaccharide in nature. Theprotective sheath provided by the glycocalyx at the infected siteeffectively prevents the elimination and treatment of these infections.As a result, microbial growth inhibiting solutions are needed that areeffective for reducing or eliminating glycocalyx of infectiousmicroorganisms typically associated with catheter colonization andinfection.

Transdermal vascular catheters get engulfed by a fibrin sheath thatsubsequently acts to cover the internal and external surfaces of acatheter. This fibrin sheath provides such organisms as Staphylococciand Candida, with an enhanced adherence capacity to the cathetersurface. Unlike these particular microbes, gram-negative bacilli do notadhere well to fibrin and fibronectin. A composition that halts fibrinformation would thus be particularly useful in halting the colonizationof Staphylococci, Candida, and the like, at transdermal catheter sites.

Ethylenediaminetetraacetic acid (“EDTA”) is an anticoagulant used inblood collection tubes. It is also recognized as a calcium chelatingagent. EDTA is also recognized to have an antibacterial andantistaphylococcal effect (alone or in combination) (Harper & Epis(1987) Microbios. 51:107; Said et al. (1987) J. Med. Microbiol. 24:267;Root et al. (1988) Antimicrob. Agents Chemother. 32:1627). While thoseinvestigators found EDTA to be bacteriocidal, no remedy or suggestion ofhow the microbial glycocalyx of a device-related infection could beeliminated was provided.

Ethylene glycol tetraacetic acid (“EGTA”) is another recognizedchelating agent. This agent has not been described as antimicrobial.Triethylene tetramine dihydrochloride (trientine 2HCl) (“TTH”) is arecognized chelating agent that chelates copper. TTH and other chelatingagents, including diethylenetriamine pentaacetic acid (“DTPA”), aresimilarly not recognized as having antimicrobial activity.

Although glycopeptide antibiotics (vancomycin and teicoplanin) areeffective against staphylococci in vitro and in tissue, they are notactive against adherent staphylococci embedded in a biofilm layer, suchas glycocalyx. While flushing with such agents may acutely destroy thesemicroorganisms, the risk of rapid development of tolerant and resistantstrains in the patient being treated makes this a contraindicatedprocedure in most cases.

U.S. Pat. No. 5,362,754 to Raad (“Raad I”) describes compositions foruse with catheters that include a tetracycline antibiotic, such asminocycline, and EDTA. Raad I teaches the use of 10-100 mg/ml of EDTA incombination with 0.001-100 mg/ml of minocycline and the more preferredcombination of 20-60 mg/ml of EDTA and 2-9 mg/ml of minocycline. U.S.Pat. No. 5,688,516 also to Raad (“Raad II”) in Example 10 teaches thatminocycline and EDTA compositions of less than 3 mg/ml EDTA areineffective at controlling all microbial growth. Raad II furtherteaches: “These studies also demonstrate the marked enhancement ofanti-Candida albicans inhibitory activity where a ratio of minocyclineto EDTA of 10:1 (10% EDTA) is used.”

U.S. Pat. Nos. 4,343,788 and 4,479,795 to R. V. Mustacich describepolymer compositions containing carboxylate antimicrobial agents forincorporation into catheters. U.S. Pat. No. 4,392,848 to D. S. Lucasdescribes polymer compositions for incorporation into catheters that arepermeable to carboxylate antimicrobial agents. U.S. Pat. No. 4,489,097to R. L. Stone (“Stone”) describes intravenous solutions containingcarboxylate antimicrobial agents, preferably n-hexanoic and n-octanoicacids and pharmaceutically-acceptable, water-soluble salts thereof.Stone teaches the use of these carboxylate antimicrobial agents tosterilize intravenous solutions and to maintain these intravenoussolutions sterile during manipulation. Administration of Stone'ssolutions as described into an intravenous catheter to “lock” thecatheter under a static (no flow) situation would result in rapidocclusion of the access due to backflow of blood into the device and thelack of anticoagulation characteristics of the described compositions.

A prophylactic agent for catheter maintenance should bothinhibit/eliminate the formation of polysaccharide-rich glycocalyx andeliminate Staphylococci and fungi. In view of the foregoing, there is aneed for improved compositions, kits and methods for flushing, lockingand disinfecting catheters. Such compositions should have antimicrobialactivity against a broad spectrum of microorganisms, preferablyincluding fungi and both gram-positive and gram-negative bacteria, andpreferably be effective against planktonic (free-floating) and adherentmicroorganisms embedded in a biofilm. The compositions should discouragethe development of resistant microbes, be relatively inexpensive,non-toxic, compatible with the catheter material, safe if inadvertentlyinfused systemically, easy to implement, require minimum or no solution,and be useful with most or all types of implanted catheters, includinghemodialysis and hemofiltration catheters, IV catheters, peritonealdialysis catheters, urinary catheters, chemotherapy catheters, and thelike. At least some of these objectives are met by embodiments of theinvention described hereinafter.

SUMMARY

Embodiments of the present invention provide unique and effectivemicrobial growth inhibiting solutions (e.g., locking solutions) thatinclude effective amounts of a carboxylate antimicrobial agent, such asa C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent or antifungal agent,and a chelating agent. In one preferred embodiment, the chelating agentis EDTA and the C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent isn-capric, n-lauric, and n-octanoic acid. In other embodiments, themicrobial growth inhibiting solutions comprise a C₄-C₉, C₁₀ or C₁₂carboxylate antimicrobial agent and a chelating agent other than EDTA. Apreferred combination includes a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent and a calcium chelating agent, such as EGTA.Chelating agents that may be used in conjunction with the presentinvention include, but are not limited to, EDTA, EGTA, DTPA,dimercaptosuccinic acid (“DMSA”), deferoxamine, dimercaprol, triethylenetetramine dihydrochloride, zinc citrate, combination of bismuth andcitrate, penicillamine, etidronate and pharmaceutically acceptable saltsthereof. Preferred chelating agents include those that chelate divalentmetal cations such as Ca, Mg, Mn, Fe and Zn.

It has been surprisingly found that a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent in combination with a chelating agent present in anamount of about 2 mg/mL, 1 mg/mL or lower can effectively inhibitmicrobial or fungal growth in a catheter. In any of the embodimentsdescribed herein, the microbial growth inhibiting solutions can includea combination of a chelating agent and a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent, wherein the concentration of the chelating agent ispresent in an amount ranging from about 0.01 to about 2 mg/mL in thesolution and the concentration of the antimicrobial agent is present inan amount ranging from about 0.05 mg/ml to about 5 mg/ml in thesolution. In a preferred embodiment, the combination includes about 0.5mg/ml of the chelating agent and about 1.15 mg/ml of the C₄-C₉, C₁₀ orC₁₂ carboxylate antimicrobial agent.

Where n-capric, n-lauric, and n-octanoic acid is the antimicrobial agentof choice, it can be reconstituted to an appropriate concentration froma vial of n-capric, n-lauric, or n-octanoic acid and then combined inthe manner described herein to provide a solution with the concentrationof n-octanoic acid desired according to methods well known to those ofordinary skill in the art of microbial growth inhibiting solutions. Thecarrier solution, by way of example, can comprise saline, phosphatebuffered saline, dextrose in water, Ringer's solution or water pHadjusted to 5.2 or less.

In an embodiment, the microbial growth inhibiting solutions include apharmacologically acceptable carrier solution, such as water, Ringer'ssolution or saline pH adjusted to 5.2 or less. The microbial growthinhibiting solutions can have an in-use pH of about 6.0, or below,generally in the range of about 3.5 to about 5.8, or most preferably inthe pH range of about 3.5 to about 5.2. Within this acidic pH range,proper concentrations of the carboxylate compounds in the free acid formquickly and efficiently kill a wide variety of bacteria and fungi.

In an embodiment, the chelating agents provide potent glycocalyxinhibiting potential. In addition, C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agents of the compositions, such as n-capric, n-lauric, orn-octanoic acid at high concentrations, preferably have a fungicidaleffect and a unique ability to penetrate a polysaccharide-richglycocalyx biofilm layer. The combination of the C₄-C₉, C₁₀ or C₁₂carboxylate antimicrobial agent and chelating agent can advantageouslyprovide anticoagulant, glycocalyx inhibiting, antibacterial andantifungal agent for the prevention of thrombogenesis, microbialadherence and device-related infections. N-capric, n-lauric, andn-octanoic acid in combination with EDTA is one example of such acombination that may be preferred for use in a kit. Chelating agentsother than EDTA that are desired include EGTA and DTPA.

In another embodiment, methods of using microbial growth inhibitingsolutions including the chelating agent with the C₄-C₉, C₁₀ or C₁₂carboxylate antimicrobial agent in a variety of therapeutic applicationsare provided. One such therapeutic application is for preventingcatheter infections. An example of a composition to be used in thepractice of these methods comprises n-capric, n-lauric, or n-octanoicacid together with a chelating agent. EDTA is an example of a chelatingagent contemplated for use in these methods; however, other chelatingagents would also be expected to be useful.

For use in maintaining catheter patency, the microbial growth inhibitingsolutions may be efficaciously used with medical devices such as acentral venous catheter, a peripheral intravenous catheter, an arterialcatheter, a Swan-Ganz catheter, a hemodialysis catheter, an umbilicalcatheter, a percutaneous nontunneled silicone catheter, a cuffedtunneled central venous catheter, as well as with a subcutaneous centralvenous port.

Embodiments of the invention also provide medical devices, such ascatheters, that are coated with any of the foregoing microbial growthinhibiting solutions. In one preferred embodiment, the microbial growthinhibiting solution comprises EDTA and n-capric, n-lauric, or n-octanoicacid. Where the chelating agent is other than EDTA, the microbial growthinhibiting solution in one example includes EGTA together with anantimicrobial agent such as n-capric, n-lauric, or n-octanoic acid.Particular exemplary medical devices that may be prepared and coatedwith the solutions of the present invention are provided in the abovelist.

Embodiments of the present invention also provide processes forpreparing coated medical devices with the compositions described herein.In an embodiment, a process comprises exposing the medical device to amicrobial growth inhibiting solution including a chelating agentcombined with a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent for asufficient amount of time to provide a coating on the exposed surface ofthe device. Where the microbial growth inhibiting solution is in aliquid form, it can be allowed to dry on the device surface to form afilm.

In a preferred embodiment of the above described processes, the deviceis first treated with a surfactant before exposing the device to themicrobial growth inhibiting solution. Such surfactants, by way ofexample, include tridodecylmethyl ammonium chloride and benzalkoniumchloride.

In another aspect, a catheter flushing solution is provided. Mostpreferably, the catheter flushing solution comprises a glycocalyxinhibiting concentration of a chelating agent and an effective amount ofa C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent in apharmaceutically acceptable carrier solution (e.g., saline pH adjustedto 5.2 or less).

In one preferred embodiment of the solution, the chelating agent is EGTAand the C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent is n-capric,n-lauric, or n-octanoic acid. Another embodiment of the catheterflushing solution includes about 0.5 mg/mL EDTA and about 1.15 mg/mln-capric, n-lauric, or n-octanoic acid. By way of example, one carriersolution is saline, water, or a Ringer's solution pH adjusted to 5.2 orless. The catheter flushing solution may advantageously be used toinhibit the formation of polysaccharide-rich glycocalyx. In this manner,infections characterized by such a formation may be effectivelyeliminated.

Another aspect of the present invention provides a method of preparing abiofilm-resistant medical device. In one embodiment, the methodcomprises exposing a device with the microbial growth inhibitingsolutions described herein. Any of a variety of catheters may be treatedor coated according to the described method employing coating techniqueswell known to those of ordinary skill in the art.

While the method may be used to coat virtually any surface whereglycocalyx formation is to be desirably inhibited, use of the method inpreparing a microbial biofilm-resistant catheter device is particularlyenvisioned. By way of example, catheters that may be prepared andtreated according to embodiments of the invention include a centralvenous catheter and a triple lumen catheter. It is anticipated that themethod will provide a device resistant to polysaccharide-rich glycocalyxformation, such as that typical of Staphylococci.

In a preferred aspect of the described method, a biofilm-resistantmedical device is prepared using a microbial growth inhibiting solutionof a chelating agent and a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent. An example of such solution comprises a combination of n-capric,n-lauric, or n-octanoic acid and EDTA, or a combination of a chelatingagent other than EDTA together with a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent. The various concentration ranges of the C₄-C₉, C₁₀or C₁₂ carboxylate antimicrobial agents and chelating agents describedabove are also contemplated as useful in the compositions for coating amedical device.

In one aspect, the method comprises preparing a microbial growthinhibiting solution of the desired combination in a biocompatibleadherent coating carrier solution. The surface of the medical device ofinterest is then exposed to the microbial growth inhibiting solution fora period of time sufficient to allow the formation of a film or coatingof the solution on the surface of the device. This may be accomplished,for example, by dipping the device in the solution. Most preferably, thedevice to be coated is a catheter. Such treatment provides abiofilm-resistant catheter.

Embodiments of the present invention also provide methods for inhibitingglycoprotein-rich glycocalyx formation at a catheter port. The method inone embodiment comprises flushing the catheter periodically with amicrobial growth inhibiting solution comprising a glycocalyx-inhibitingconcentration of a chelating agent and a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent in a pharmacologically acceptable carrier solution.

The described methods can be used to inhibit infection at virtually anytunneled or untunneled catheter. As part of a catheter maintenanceregimen, the catheter most preferably is to be flushed with acomposition comprising a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent and a chelating agent in a pharmaceutically acceptable carriersolution. The described regimen is repeated once a week, once every 4days, once every 2 days, once a day (about every 24 hours), twice a day,every four hours or as needed according to patient needs.

In still another aspect, embodiments of the invention provide methodsfor eliminating microbial glycocalyx formation, particularlypolysaccharide-rich (Staphylococcal) glycocalyx formation, at a catheterlumen. The method, in one embodiment, comprises preparing a microbialgrowth inhibiting solution comprising a chelating agent (e.g., EDTA,EGTA, or both) together with a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent (e.g., n-butyric, n-pentanoic, n-hexanoic,n-heptanoic, n-octanoic n-capric, n-lauric, or n-nonanoic acids and/orpharmaceutically acceptable salts thereof) in a carrier solution toprovide a flushing composition, and flushing the catheter with an amounteffective to inhibit microbial growth of the flushing composition.

Most preferably, the catheter will be flushed with a volume of about 3mL of the described n-capric, n-lauric, or n-octanoic acid and EDTAsolution containing about 0.5 mg/mL EDTA and about 1.15 mg/ml n-octanoicacid. The catheter can be flushed periodically at intervals of once aweek, once every 4 days, once every 2 days, once a day, twice a day,every four hours, or as needed according to patient needs with about 2-3mL of the n-capric, n-lauric, or n-octanoic acid and EDTA solution. Thecatheter flushing regimen may simply constitute once every time that thecatheter is used or changed. In a preferred aspect of the method, thecatheter is to be flushed at 4 hour intervals with the herein describedsolutions.

The compositions describe herein preferably remain therapeuticallyeffective for use as a catheter-flushing agent after storage at arefrigerated temperature. However, the n-capric, n-lauric, or n-octanoicacid and EDTA solution should be brought to room temperature before useon an animal or patient.

The present invention in still another aspect provides a kit. In oneembodiment, the kit comprises a container, such as a syringe, holding avolume of one of the foregoing solutions containing a C₄-C₉, C₁₀ or C₁₂carboxylate antimicrobial agent and a chelating agent and an implantablecatheter lumen to receive the solution. The kit may further comprise apackage, such as a box, tray, tube, envelope, pouch, or the like, forholding the container. The volume of the solution in the container istypically in the range from 1 mL-20 mL, preferably from 2 mL-10 mL,usually being about 2 mL-4 mL. Optionally, the container will usuallycomprise a syringe, or device to permit direct introduction of thesolution into the indwelling catheter.

In another embodiment, the kit comprises a container, such as acompartmentalized syringe, that comprises a plurality of compartments.For example, the container can have three compartments, where onecompartment comprises a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent, such as n-capric, n-lauric, n-octanoic acid; the secondcompartment comprises a chelating agent, such as EDTA; and the thirdcompartment comprises a diluent, such as saline, Ringer's solution, orwater pH adjusted to 5.2 or less. Kits that include a carrier adapted toreceive at least two compartments constitute still another embodiment ofthe kit. In these embodiments, the chelating agent would be includedtogether with the C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agentwithin a compartment of the container. The second compartment wouldcomprise a diluent, such as the ones described above. In an embodiment,the chelating agent and antimicrobial agent are included together in afirst compartment of the device in dry powder form. The dry componentswould preferably be combined with the diluent of a second compartment toprovide a solution suitable for use.

In these various embodiments, the kit preferably includes a chelatingagent. In particular embodiments, the chelating agent is EDTA, and theC₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent is, by way of example,n-capric, n-lauric, or n-octanoic acid.

In yet another aspect of the present invention, a method fordisinfecting an implanted catheter is provided that includes introducinga solution comprising a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent and a chelating agent in a pharmaceutically acceptable carriersolution into a lumen of a catheter where at least a portion of thecatheter is sufficiently porous to permit diffusion of the solutionoutwardly from the lumen to the outer surface of the catheter and intothe tissues or the bloodstream surrounding the catheter to inhibitinfection. The implanted catheter may be a subcutaneous ortranscutaneous indwelling catheter.

The ability to inhibit or prevent infection of the implanted cathetercan be improved by utilizing catheters where at least a portion of thecatheter body is sufficiently porous to allow the antimicrobial lockingsolution to permeate the catheter body and, preferably, pass outwardly(i.e., seep, ooze, leak, diffuse) into the tissue region surrounding thecatheter. While the use of such porous or partially porous catheterbodies can be beneficial with many antimicrobial locking solutions, suchas those taught in U.S. Pat. Nos. 4,186,745; 4,767,400; 4,968,306;5,077,281; 5,913,856; 6,949,087; 7,004,923; and U.S. Patent PublicationNos. 2006/0074388 and 2006/0253101, it is particularly useful with theacids of the present invention. It will be appreciated that C₄-C₉, C₁₀or C₁₂ carboxylate antimicrobial agents have molecular weights and otherqualities that enable them to readily penetrate into and through manyporous materials. Exemplary porous materials for construction of thecatheter body include silicone rubber, expanded PTFE (e.g., GORE-TEXmedical membranes), TEFLON® films, natural, regenerated orsemi-synthetic cellulosic materials such as cellulose acetate, cellulosediacetate, cuprophane, and the like. Such materials may be formed intothe tubular catheter bodies or may be incorporated as separatecomponent(s) into the catheter bodies.

The described microbial growth inhibiting solutions are expected to beeffective in preventing the adherence and colonization of cathetersurfaces by S. aureus, S. epidermidis, and fungi, as well as effectivein both treating and eliminating already formed glycocalyx formations ofthese infectious organisms.

It is contemplated that whenever appropriate, any embodiment of thepresent invention can be combined with one or more other embodiments ofthe present invention, even though the embodiments are described underdifferent aspects or embodiments of the present invention. Additionalfeatures and advantages are described herein, and will be apparent from,the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 A and 1B illustrate methods according to the present inventionfor locking and disinfecting a transcutaneous catheter.

FIGS. 2A-2C illustrate methods according to the present invention forflushing, locking and disinfecting a subcutaneously implanted catheter.

FIGS. 3A-3C illustrate methods according to the present invention forflushing, locking and disinfecting a peritoneal dialysis catheter.

FIG. 4 illustrates an embodiment of the present invention where anantimicrobial locking solution permeates into an implanted catheter bodyand preferably into the tissue surrounding the catheter body.

FIG. 5 illustrates a kit constructed in accordance with the principlesof the present invention.

FIG. 6 shows a comparison of Na Octanoate/EDTA and Heparin by a PTT.

DETAILED DESCRIPTION

The details of one or more embodiments of the invention are set forth inthe accompanying description below. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, the methods and materialsare now described. Other features, objects, and advantages of theinvention will be apparent from the description. In the specification,the singular forms also include the plural unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. In the case of conflict, the present Specification willcontrol.

DEFINITIONS

The terms below have the following meanings unless indicated otherwise.

The term “biofilm” as used herein refers to a polysaccharide-richglycocalyx that typically accompanies microbial surface colonization.

As used herein, a “biofilm-resistant” device or surface is a surface ordevice that will prevent the adherence or growth of organisms thatproduce polysaccharide-rich glycocalyx material. Such organisms include,but are not limited to, the Staphylococcus aureus and S. epidermidisspecies.

The term “glycocalyx inhibiting concentration” as used herein refers toa concentration effective to degrade, dissolve, or otherwise inhibit apolysaccharide-rich glycocalyx. By way of example, such apolysaccharide-rich glycocalyx is characteristic of establishedstaphylococcal infections of S. aureus and S. epidermidis.

As used herein, the terms “implanted”, “subdermal”, “subcutaneous” and“indwelling” are used synonymously to refer to the placement of amedical device, for example, a catheter. These implanted catheterstypically will have a distal end which is at least partially open to abody lumen. Most commonly, the catheters will be intravascular catheterswhere the distal end is implanted in or attached to a bloodvessel—usually a vein, but in some cases an artery. Exemplaryintravascular catheters include hemodialysis and hemofiltrationcatheters, as well as intravenous catheters. Intravenous catheters canbe used for a wide variety of purposes, including fluid infusion anddrug delivery. Catheters attached other than to the vasculature includeperitoneal dialysis catheters which are open to the peritoneal cavityand urinary catheters which open to the bladder.

The medical devices, such as catheters, which are described herein maybe transcutaneously implanted or subcutaneously implanted. By“transcutaneously implanted,” it is meant that the distal end of thecatheter is attached to or implanted within a target body lumen and aproximal end of the catheter is located externally to the patient. Anintermediate portion of the catheter will thus pass through or penetratethe patient's skin, and the proximal end of the catheter will usuallyhave a hub to permit selective attachment of infusion tubes, syringes,solution bags, and the like. Most commonly, the proximal attachment hubwill have a luer fitting. By “subcutaneously implanted,” it is meantthat the entire catheter is implanted beneath the skin and no portion ofthe catheter extends through the skin. Such subcutaneously implantedcatheters are typically attached to a fully implanted hub at theirproximal ends. The hub permits percutaneous access via a needle or otherpenetrating element.

Embodiments of the present invention provide microbial growth inhibitingsolutions of C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agents incombination with chelating agents. These microbial growth inhibitingsolutions are expected to be particularly useful in preventing theformation of the “biofilm” or polysaccharide-rich glycocalyx thattypically accompanies microbial surface colonization. In particular, themicrobial growth inhibiting solutions are expected to be most effectivein breaking down staphylococcal glycocalyx and in inhibiting itsformation. This feature renders the microbial growth inhibitingsolutions of the present invention particularly useful in the treatmentof staphylococcal infections where a polysaccharide-rich glycocalyx hasformed or may potentially be formed, as well as in the prevention andtreatment of Staphylococcus and Candida infection.

Embodiments of the present invention also provide treated or coatedmedical devices, such as catheters, that prevent staphylococcal orfungal colonization. The coating or film provided on these devicescomprises a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent, such asn-capric, n-lauric, or n-octanoic acid, and a chelating agent. Aparticular preferred combination of ingredients of the microbial growthinhibiting solutions includes n-capric, n-lauric, or n-octanoic acid andEDTA. Other preferred combinations comprise a glycocalyx inhibitingconcentration or amount of a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent and a chelating agent other than EDTA. Devices coated with thesecombinations of agents are also envisioned to be useful.

Antimicrobial Agents

The C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agents used in any ofthe microbial growth inhibiting solutions and methods described hereincan include non-aromatic water-soluble C₄-C₉, C₁₀ or C₁₂ alkyl, alkenylor alkynyl organic acids, or mixtures thereof, or any of theirwater-soluble, pharmaceutically-acceptable salts. Such salts include,for example, sodium, potassium and ammonium salts. The sodium andpotassium salts are preferred.

While the various carboxylate compounds exhibit different degrees ofantimicrobial activity (per mole), water-soluble agents having theformula: R—COOH, wherein R═C₃-C₈, C₉ or C₁₁ n-alkyl, as well aspharmaceutically acceptable salts thereof or a combination thereof,exhibit excellent antimicrobial activity. The n-capric, n-lauric,n-hexanoic and n-octanoic acids and pharmaceutically-acceptable,water-soluble salts thereof are much preferred, with n-capric, n-lauric,or n-octanoic acid being more preferred. These materials in their freeacid form rapidly kill essentially all important gram positive and gramnegative pathogens, and Candida, at low solution concentrations in theacid pH range.

The microbiocidal activity of the C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobials is directly related to the presence of their respectivefree acids in solution. The concentration of free carboxylic acid insolution, as opposed to carboxylate salt (anionic) form, is a functionof the solution pH. Carboxylic acid salts can be used, but only as longas the solution pH is such that a minimum lethal concentration (“MLC”)of free acid is present. Accordingly, the amount of acid or acid saltused will vary somewhat with the use pH. The amount of a given acid saltor acid that will provide the MLC at a given pH will depend on thepK_(a) of the acid. Of course, knowing the pK_(a), the MLC of theparticular acid and the use pH, the amount of any C₄-C₉, C₁₀ or C₁₂ acidor acid salt to be used is easily calculated from the following formula:

pK_(a)=pH+log([HC_(x)]/[C_(x-)]),

where [HC_(x)] is the concentration of free acid of chain length x and[C_(x-)] is the concentration of its anion.

In an embodiment, the antimicrobial agent is present in an amountranging from about 0.05 mg/ml to about 5 mg/ml in the microbial growthinhibiting solution. More specifically, the amount of the antimicrobialagent can be about 0.05 mg/mL, 0.1 mg/mL, 0.25 mg/mL, 0.5 mg/mL, 0.75mg/mL, 1 mg/mL, 1.25 mg/mL, 1.5 mg/mL, 1.25 mg/mL, 2 mg/mL, 2.25 mg/mL,2.5 mg/mL, 2.75 mg/mL, 3 mg/mL, 3.25 mg/mL, 3.5 mg/mL, 3.75 mg/mL, 4mg/mL, 4.25 mg/mL, 4.5 mg/mL, 4.75 mg/mL, 5 mg/mL and the like. Itshould be appreciated that any two amounts of the antimicrobial agentrecited herein can further represent end points in a therapeuticallypreferred range of the antimicrobial agent. For example, the amounts of0.5 mg/mL and 1.5 mg/mL can represent the individual amounts of theantimicrobial agent as well as a preferred range of the antimicrobialagent in the solution from about 0.5 mg/mL to about 1.5 mg/mL.

Chelating Agents and Buffers

In addition to the C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agents,the microbial growth inhibiting solutions and methods described hereinalso include one or more chelating agents. Any of the microbial growthinhibiting solutions and methods described herein can also include oneor more suitable buffers. Non-limiting examples of suitable chelatingagents and buffers that can be used in various embodiments of thepresent invention can be selected from Tables 1 and 2, respectively.Pharmaceutically acceptable salts (e.g., edetate calcium disodium) ofany chelating agents listed in Table 1 can also be used.

TABLE 1 CHELATING AGENTS Deferoxamine Dimercaprol EDTA EGTA DTPA DMSAPenicillamine Dimercaptosuccinic acid

TABLE 2 BUFFERING AGENTS Acetate-Acetic acid Citrate-Citric acidPhosphate-Phosphoric acid Tartrate-Tartaric acid Malate-Malic acidFumarate-Fumaric acid Malonate-Malonic acid Barbiturate-barbituric acid

In certain preferred embodiments, the C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agents are combined with EDTA. EDTA is available ascalcium disodium EDTA and sodium EDTA formulations. A preferred form issodium EDTA.

In alternative embodiments, the C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agents are combined with chelating agents other than EDTA.Where administration of too much locking solution or administration ofthe locking solution too quickly would produce calcium complexationleading to hypocalcemia potentially resulting in ventricular arrhythmiasand sudden death, use of such a chelating agent in high concentrationswould be undesirable.

As will be appreciated by those of skill in the art, the foregoing listsare only intended to be exemplary. Other chelating agents, as well asbuffers, are also expected to be useful and effective in combinationwith a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent. Thesecombinations formulated as a coating will preferably further include amaterial, such as a cationic surfactant (e.g., tridodecylmethyl ammoniumchloride or benzalkonium chloride), that will enhance adherence or filmforming characteristics, of the solution. As a solution for flushing orother medicinal use, the ingredients will be suspended in a carriersolution such as sterile saline, phosphate buffered saline, dextrose inwater, Ringer's solution, distilled water or any other physiologicallyacceptable solution pH adjusted to 5.2 or less.

In an embodiment, the chelating agent is present in an amount rangingfrom about 0.01 mg/mL to about 2 mg/mL in the microbial growthinhibiting solution. More specifically, the amount of the chelatingagent can be about 0.01 mg/mL, 0.05 mg/mL, 0.1 mg/mL, 0.15 mg/mL, 0.2mg/mL, 0.25 mg/mL, 0.3 mg/mL, 0.35 mg/mL, 0.4 mg/mL, 0.45 mg/mL, 0.5mg/mL, 0.55 mg/mL, 0.6 mg/mL, 0.65 mg/mL, 0.7 mg/mL, 0.75 mg/mL, 0.8mg/mL, 0.85 mg/mL, 0.9 mg/mL, 0.95 mg/mL, 1 mg/mL, 1.05 mg/mL, 1.1mg/mL, 1.15 mg/mL, 1.2 mg/mL, 1.25 mg/mL, 1.3 mg/mL, 1.35 mg/mL, 1.4mg/mL, 1.45 mg/mL, 1.5 mg/mL, 1.55 mg/mL, 1.6 mg/mL, 1.65 mg/mL, 1.7mg/mL, 1.75 mg/mL, 1.8 mg/mL, 1.85 mg/mL, 1.9 mg/mL, 1.95 mg/mL, 2 mg/mLand the like. It should be appreciated that any two amounts of thechelating agent recited herein can further represent end points in atherapeutically preferred range of the chelating agent. For example, theamounts of 0.2 mg/mL and 0.5 mg/mL can represent the individual amountsof the chelating agent as well as a preferred range of the chelatingagent in the solution from about 0.2 mg/mL to about 0.5 mg/mL.

Methods of Flushing, Locking and Disinfecting a Catheter

Referring now to FIGS. 1A and 1B, methods according to embodiments ofthe present invention for locking an implanted venous catheter 10 willbe described. The venous catheter 10 will be implanted through apatient's skin S into a vein V for infusion of the patient. When it isdesired to disconnect the patient from the source of infusion, it willbe necessary to lock the catheter to inhibit plugging and fouling causedby coagulation, and preferably to further inhibit or eliminate the riskof infection. Shown in FIG. 1A, a tube 12 containing an IV solution willnormally be connected to the proximal hub 14 of the catheter 10. The IVline 12 will be disconnected, and the catheter 10 rinsed with a flushingsolution. After flushing is completed, a locking solution of a C₄-C₉,C₁₀ or C₁₂ carboxylate antimicrobial agent and a chelating agent isintroduced to fill the inner lumen of the catheter 10, as shown in FIG.1B. Usually, a sufficient volume of the locking solution will beintroduced to completely fill the lumen of the implanted catheter 10,with minimum excess passing from distal end 16 of the catheter. The lossof excess solution into a blood vessel or most other body lumens,however, will generally not be a problem. The “column” of the solutionwill then occupy the inner lumen, and the proximal hub will be sealed,helping retain the solution in place. The locking solution of a C₄-C₉,C₁₀ or C₁₂ carboxylate antimicrobial agent and a chelating agent willeffectively inhibit clotting and coagulation at the distal end 16 aswell as inhibit or eliminate infection throughout the catheter. When itis desired to reattach the patient to the IV source, the solution willbe removed and the catheter lumen flushed.

Referring now to FIGS. 2A-2C, flushing and locking of a subcutaneouslyimplanted catheter 20 used for hemodialysis access will be described.The catheter 20 is implanted between a target blood vessel BV, typicallya vein, and an implanted port 22. During hemodialysis, blood iswithdrawn through the catheter 20, through the port 22 and externallythrough a needle N and connecting line 23 used to percutaneously accessthe port 22 (FIG. 2A). Alternatively, the port and catheter can used toreturn treated blood to the patient.

When it is desired to end a hemodialysis (or hemofiltration) treatment,a flushing solution (“FS”) of a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent and a chelating agent will be introduced through theneedle N (typically from a syringe which is attached to the connectingline 23) to flush the lumen, as depicted in FIG. 2B. After the flush iscomplete, a locking solution is injected from a container such as asyringe 26 through the line 23/port 22 and into the lumen of catheter 20to displace the flushing solution and lock the catheter (FIG. 2C). Thelocking solution will remain in place within the catheter 20.Alternatively or additionally, the locking solution can be a solution ofa C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent and a chelatingagent.

The methods of the present invention may also be used to flush and locknon-vascular catheters, such as peritoneal dialysis catheters 30, asshown in FIGS. 3A-3C. After a peritoneal dialysis treatment, the useddialysate is withdrawn from the catheter 30, as shown in FIG. 3A. Afterthe dialysate has been sufficiently removed, the dialysis catheter 30 isflushed with a flushing solution FS of a C₄-C₉, C₁₀ or C₁₂ carboxylateantimicrobial agent and a chelating agent, as shown in FIG. 3B. Afterflushing, the locking solution is introduced to the peritoneal dialysiscatheter 30, as shown in FIG. 3C, so that it fills the lumen of thecatheter, as described previously with the vascular catheters.Alternatively or additionally, the locking solution can be a solution ofa C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent and a chelatingagent.

Referring now to FIG. 4, the use of a locking solution containing aC₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobial agent and a chelating agentcan be enhanced by utilizing an implanted catheter which is formed atleast partly from a porous material. When the lumen 40 of the porouscatheter body 42 is filled with a solution containing a C₄-C₉, C₁₀ orC₁₂ carboxylate antimicrobial agent and a chelating agent, the solutionwill be able to slowly penetrate (i.e., seep) into the catheter body andoutwardly into the tissue T surrounding the catheter, as shown by thearrows in FIG. 4. Thus, the antimicrobial properties of the lockingsolution will not be entirely limited to the interior lumen of thecatheter, but will also be effective on the surface of the catheter andin the tissue region immediately surrounding the catheter body.Particularly suitable materials and porosity properties for the catheterbodies have been set forth above.

Referring now to FIG. 5, kits according to the present invention willinclude at least a container 60, such as a syringe, for holding a volumeof a locking solution of a C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagent and a chelating agent and an implantable catheter lumen to receivethe solution. The volume will typically be within the ranges set forthherein. The kits can further contain a package 62 to hold the container60. The package can be any conventional medical device package,including boxes, tubes, envelopes, trays and pouches. In addition, thekit can contain instructions for use (“IFU”) setting forth a method forlocking and/or disinfecting an implanted catheter by introducing thesolution from the container into a lumen of the implantable catheterbetween successive uses of the catheter.

EXAMPLES

The present invention is further defined in the following Examples. Itshould be understood that these Examples, while indicating preferredembodiments of the invention, arc given by way of illustration only.From the above discussion and these Examples, one skilled in the art canascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various uses andconditions.

Example 1 Evaluation of Microbial Growth Inhibiting Solutions

The following studies provided antimicrobial/antifungal testing offormulated microbial growth inhibiting solutions according to thepresent disclosure.

Methicillin-Resistant Staphylococcus Aureus (“MRSA”)

A stock culture of Staphylococcus aureus was maintained as a frozenstock culture at −70° C. until use. The bacterial testing usedStaphylococcus aureus isolated from human blood. A cell suspension wasprepared from the frozen stock culture and cultivated in tryptic soybroth (“TSB”) to yield approximately 1×10⁸ colony forming units (“CFU”)per milliliter for MRSA. The final concentration of the inoculumsolution was confirmed using plate counts.

Bacterial testing—For the test, 9.9 ml of each test solution wasinoculated with 100 ul of the MRSA cell suspension to yield a final cellconcentration of approximately 1×10⁶ CFU/ml. This represents a 1:100dilution of the starting 1×10⁸ CFU/ml culture; the initial cellconcentration was calculated based on the inoculum plate count. Eachtest or control solution was evaluated in triplicate. Samples werecollected at T=1 hour.

Sampling of treated organisms for growth—Each sample was seriallydiluted in PBS (pH 7.0) and plated in duplicate on tryptic soy agar(“TSA”) plates. All plates were incubated inverted at 37° C. for 24hours. For the remaining volume of the treated sample: 1) Each samplewas filtered through a 0.22 μm filter membrane, and 2) Each filter wasrinsed with 15 ml sterile water. The filter was placed directly onto aTSA plate and incubated without inversion for 24 hr at 37° C.

Analyses—The CFU/ml for each solution was logarithmically transformed(base 10). In cases where the plate counts were zero, a value of 0.5 wassubstituted for one of the zero counts. This substituted value wasscaled, based on the dilution plated or volume filtered. The results ofthree experiments were averaged to determine the mean log density andthe associated standard deviation was calculated. Log reductions werecalculated for the cultures treated with locking solution by subtractingthe mean log density at 24 hrs from that at time zero.

Pseudomonas aeruginosa

Pseudomonas aeruginosa (a representative gram negative bacterium) wasgrown to a defined log phase growth in culture. Representative samplesof the culture were incubated/treated for a defined time with variousvehicle (solvent) or locking solutions. Aliquots of the treated sampleswere plated on agar plates and colony counts performed after sufficienttime for growth to assess the efficacy of the lock in killing theorganisms of interest.

Bacterial strain and solution of cultures—A stock culture of Pseudomonasaeruginosa to be tested was maintained as a frozen stock culture at −70°C. until use. The bacterial testing used Pseudomonas aeruginosa isolatedfrom human blood. A cell suspension was prepared from the frozen stockculture and cultivated in TSB to yield approximately 1×10⁸ CFU permilliliter for P. aeruginosa. For reference, a 0.5 McFarland unit willtypically reflect this approximate number of organisms. The finalconcentration of the inoculum solution was confirmed using plate counts.

Bacterial testing—For the test, 9.9 ml of each test solution wasinoculated with 100 ul of the P. aeruginosa cell suspension to yield afinal cell concentration of approximately 1×10⁶ CFU/ml. Note that thisrepresents a 1:100 dilution of the starting 1×10⁸ CFU/ml culture. Theinitial cell concentration was calculated based on the inoculum platecount. Each test or control solution was evaluated in triplicate.Samples were collected at T=1 hour. Each sample was serially diluted inPBS (pH 7.0) and plated in duplicate on TSA plates. All plates wereincubated inverted at 37° C. for 24 hours. For the remaining volume ofthe treated sample: 1) each sample was filtered through a 0.22 μm filtermembrane, and 2) each filter was rinsed with 15 ml sterile water. Thefilter was placed directly onto a TSA plate and incubated (withoutinversion) for 24 hrs at 37° C.

Analyses—The CFU/ml for each solution was logarithmically transformed(base 10). In cases where the plate counts were zero, a value of 0.5 wassubstituted for one of the zero counts. This substituted value wasscaled, based on the dilution plated or volume filtered. The results ofthree experiments were averaged to determine the mean log density andthe associated standard deviation was calculated. Log reductions werecalculated for the cultures treated with locking solution by subtractingthe mean log density at 24 hrs from that at time zero.

Candida albicans

Candida albicans (a representative fungus/yeast) was grown to a definedlog phase growth in culture. Representative samples of the culture wereincubated/treated for a defined time with various vehicle (solvent) orlocking solutions. Aliquots of the treated samples were plated on agarplates and colony counts performed after sufficient time for growth toassess the efficacy of the locking solution in killing the organisms ofinterest.

A stock culture of Candida albicans ATCC was maintained as a frozenstock culture at −70° C. until use. The bacterial testing used Candidaalbicans ATCC #90028 isolated from human blood. A cell suspension wasprepared from the frozen stock culture and cultivated in TSB to yieldapproximately 1×10⁸ CFU per milliliter for C. albicans. For reference, a0.5 McFarland unit will typically reflect this approximate number oforganisms. The final concentration of the inoculum solution wasconfirmed using plate counts.

Bacterial testing—For the test, 9.9 ml of each test solution wasinoculated with 100 ul of the C. albicans cell suspension to yield afinal cell concentration of approximately 1×10⁶ CFU/ml. Note that thisrepresents a 1:100 dilution of the starting 1×10⁸ CFU/ml culture. Theinitial cell concentration was calculated based on the inoculum platecount. Each test or control solution was evaluated in triplicate.Samples were collected at T=1 hour.

Sampling of treated organisms for growth—Each sample was seriallydiluted in PBS (pH 7.0) and plated on TSA plates. All plates were platedin duplicate and incubated inverted at 37° C. for 24 hours. For theremaining volume of the treated sample: 1) each sample was filteredthrough a 0.22 μm filter membrane, and 2) each filter was rinsed with 15ml sterile water. The filter was placed directly onto a TSA plate andincubated (without inversion) for 24 hr at 37° C.

Analyses—The CFU/ml for each solution was logarithmically transformed(base 10). In cases where the plate counts were zero, a value of 0.5 wassubstituted for one of the zero counts. This substituted value wasscaled, based on the dilution plated or volume filtered. The results ofthree experiments were averaged to determine the mean log density andthe associated standard deviation was calculated. Log reductions werecalculated for the cultures treated with locking solution by subtractingthe mean log density at 24 hrs from that at time zero. Table 3 shows thesummary of results for study 1.0 discussed above.

TABLE 3 Summary of Study 1.0 Disodium Citrate Sodium Candida albicansMRSA Pseudomonas aeruginosa EDTA Buffer Caprylate D5W ATCC #90028 ATCC#700699 ATCC #27853 Solution mg/mL mM mg/mL 1/4NS CFU* CFU* CFU* 10.0625 1.5 0.071 TNTC TNTC 486 2 0.125 3 0.143 TNTC TNTC 50 3 0.25 60.287 TNTC TNTC 243 4 QS TNTC TNTC TNTC 5 0.5 12 0.575 0  0 1 6 1.0 241.15 0 40 0 7 48 TNTC TNTC 84 Positive 1.8 × 10⁷ 1.19 × 10⁸ 1.27 × 10⁸Control Final pH: 5.0 Reported values are average of three samples *CFU:Colony forming units TNTC: Too numerous to count

TABLE 4 Study 2.0 Concentration Summary Disodium Citrate Sodium SolutionEDTA Buffer Caprylate Final pH: 4.8 Lot # mg/mL mM mg/mL 1 0906301 0.525 0 2 0906302 0.5 25 1.15

TABLE 5 Summary of Study 2.0 Staph aureus Enterococcus fecalis VRE,Antibiotic Sensitive Staph epidermidis Antibiotic Resistant Escherichiacoli Klebsiella pneumoniae Serratia marcescens ATCC #6538 ATCC #12228ATCC #700802 ATCC #8739 ATCC #BAA-1705 ATCC #8100 Solution CFU* CFU*CFU* CFU* CFU* CFU* 1 7.3 × 10⁵ 4.5 × 10⁵ 1.9 × 10⁶ 1.58 × 10⁶ 7.0 × 10⁵3.3 × 10⁶ 2 0 0 0 0 13 0 Positive 2.9 × 10⁸ 1.2 × 10⁸ 2.9 × 10⁸  1.4 ×10⁸ 1.1 × 10⁸ 2.9 × 10⁸ Control Reported values are average of threesamples *CFU: Colony forming units TNTC: To numerous to count

The protocols for Staphylococcus aureus, Staphylococcus epidermidis,Enterococcus fecalis VRE, Escherichia coli, Klebsiella pneumoniae, andSerratia marcescens were similar or identical except for themicroorganism tested. It is clear from study 1.0 that sodium caprylateat a concentration of 0.575 mg/mL and disodium EDTA at a concentrationof 0.5 mg/mL pH adjusted to 5.0 with a citrate buffer was effective fora 7-8 log reduction of major medically important microorganisms. Inaddition, sodium caprylate and disodium EDTA at a concentration as lowas 0.0625 mg/mL pH was effective for a 6-7 log reduction of at least onemedically important microorganism (e.g., Pseudomonas aeruginosa).Overall, study 1.0 demonstrated that the microbial growth inhibitingsolutions having a C₄-C₉ carboxylate antimicrobial agent and a chelatingagent were synergistic at concentrations of 1 mg/mL chelating agent orlower.

As shown in Tables 4-5 (study 2.0), disodium EDTA in a citrate buffer atthe reported concentration resulted in a 2 log reduction but was notcapable of complete kill of the tested organisms. However, the additionof 1.15 mg/mL of sodium caprylate to the base disodium EDTA citratebuffer resulted in an 8 log reduction of test organisms. While sodiumcaprylate is used in the studies represented in Tables 4-5, it should beunderstood that any of the C₄-C₉, C₁₀ or C₁₂ carboxylate antimicrobialagents described herein would produce the same results. In anotherembodiment, the C₄, C₆, C₈, C₁₀ and C₁₂ carboxylate antimicrobial agentswould produce the same results as shown by the example using sodiumcaprylate.

From studies 1.0 and 2.0, the effective concentrations of the chelatingagent evaluated were well below previously reported concentrations andat a concentration that could greatly reduce the potential risk ofsudden cardiac death associated at higher dosages. In addition, theevaluated microbial growth inhibiting solutions were capable ofmaintaining intravenous catheters in the “Locked” no flow state at thecomposition proposed as demonstrated in FIG. 6.

At concentrations of microorganisms one might expect to see inindwelling intravenous access devices, it was concluded that themicrobial growth inhibiting solutions having concentrations of chelatingagents according to the invention were capable of maintaining thesedevices and effectively reducing or eliminating the microorganisms as asource of systemic infection.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

What is claimed:
 1. A microbial growth inhibiting solution comprising aC₁₀ or C₁₂ carboxylate antimicrobial agent and an agent that is achelator and a buffer, wherein the C₁₀ or C₁₂ carboxylate antimicrobialagent is present in an amount ranging from about 0.05 mg/mL to about 5mg/mL, wherein the agent that is a chelator and a buffer is citrate andis present in an amount ranging from about 1 mg/mL to about 200 mg/mL,and wherein the solution has a pH of 5.2 or less.
 2. The microbialgrowth inhibiting solution of claim 2 further comprising an additionalchelating agent selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 3.The microbial growth inhibiting solution of claim 2, wherein theadditional chelating agent chelates Ca, Mg, Mn, Fe or Zn.
 4. Themicrobial growth inhibiting solution of claim 2, wherein the additionalchelating agent is present in an amount ranging from about 0.1 mg/mL toabout 2 mg/mL.
 5. The microbial growth inhibiting solution of claim 2,wherein the additional chelating agent is present in an amount rangingfrom about 0.25 mg/mL to about 0.5 mg/mL.
 6. The microbial growthinhibiting solution of claim 1, wherein the C₁₀ or C₁₂ carboxylateantimicrobial agent is selected from the group consisting of: agentshaving the formula R—COOH wherein R═C₉ or C₁₁ n-alkyl, pharmaceuticallyacceptable salts thereof and combinations thereof.
 7. The microbialgrowth inhibiting solution of claim 1, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is selected from the group consisting ofn-capric acid, n-lauric acid, pharmaceutically acceptable salts thereofand combinations thereof.
 8. The microbial growth inhibiting solution ofclaim 1 further comprising a pharmacologically acceptable carriersolution.
 9. The microbial growth inhibiting solution of claim 8,wherein the pharmacologically acceptable carrier solution comprisessaline, Ringer's solution, or water pH adjusted to 5.2 or less.
 10. Themicrobial growth inhibiting solution of claim 1 further comprising anadditional chelating agent present in an amount ranging from about 0.1mg/mL to about 2 mg/mL wherein the C₁₀ or C₁₂ carboxylate antimicrobialagent is present in an amount ranging from about 0.071 mg/mL to about1.15 mg/mL.
 11. The microbial growth inhibiting solution of claim 10,wherein the C₁₀ or C₁₂ carboxylate antimicrobial agent comprises sodiumcaprate or socium laurate and the additional chelating agent comprisesdisodium ethylenediaminetetraacetic acid.
 12. A method of disinfectingan implanted catheter from bacteria and fungi, the method comprising:introducing to a lumen of a catheter a microbial growth inhibitingsolution comprising a C₁₀ or C₁₂ carboxylate antimicrobial agent and achelating agent, wherein the C₁₀ or C₁₂ carboxylate antimicrobial agentis present in an amount ranging from about 0.05 mg/mL to about 5 mg/mLand the chelating agent is present in an amount ranging from about 0.01mg/mL to about 2 mg/mL, and wherein the solution has a pH of 5.2 orless.
 13. The method of claim 12, wherein at least a portion of thecatheter is sufficiently porous to permit diffusion of the solutionoutwardly from the lumen to the outer surface of the catheter and intotissues or the bloodstream surrounding the catheter to inhibitinfection.
 14. The method of claim 12, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is selected from the group consistingof: agents having the formula R—COOH wherein R═C₉ or C₁₁ n-alkyl,pharmaceutically acceptable salts thereof and combinations thereof. 15.The method of claim 12, wherein the C₁₀ or C₁₂ carboxylate antimicrobialagent is selected from the group consisting of n-capric acid, n-lauricacid, pharmaceutically acceptable salts thereof and combinationsthereof.
 16. The method of claim 12, wherein the chelating agent isselected from the group consisting of ethylenediaminetetraacetic acid,diethylenetriamine pentaacetic acid, ethylene glycol tetraacetic acid,etidronate, dimercaptosuccinic acid, deferoxamine, dimercaprol,triethylene tetramine dihydrochloride, zinc citrate, combination ofbismuth and citrate, penicillamine, pharmaceutically acceptable saltsthereof and combinations thereof.
 17. The method of claim 12, whereinthe microbial growth inhibiting solution further comprises a bufferpresent in an amount ranging from about 1.5 to about 24 mM, wherein theC₁₀ or C₁₂ carboxylate antimicrobial agent is present in an amountranging from about 0.071 mg/mL to about 1.15 mg/mL, and the chelatingagent is present in an amount ranging from about 0.0625 mg/mL to about 1mg/mL.
 18. The method of claim 17, wherein the C₁₀ or C₁₂ carboxylateantimicrobial agent comprises sodium caprate or socium laurate, thebuffer comprises citrate, and the chelating agent comprises disodiumethylenediaminetetraacetic acid.
 19. A method for coating a medicaldevice, the method comprising: exposing the medical device to amicrobial growth inhibiting solution for a sufficient amount of time toprovide a coating on the exposed surface of the device, wherein themicrobial growth inhibiting solution comprises a C₁₀ or C₁₂ carboxylateantimicrobial agent and a chelating agent, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is present in an amount ranging fromabout 0.05 mg/mL to about 5 mg/mL and the chelating agent is present inan amount ranging from about 0.01 mg/mL to about 2 mg/mL, and whereinthe solution has a pH of 5.2 or less.
 20. The method of claim 19 furthercomprising treating the device with a surfactant before exposing thedevice to the microbial growth inhibiting solution.
 21. The method ofclaim 20, wherein the surfactant is selected from the group ofsurfactant consisting of tridodecylmethyl ammonium chloride,benzalkonium chloride and combinations thereof.
 22. The method of claim19, wherein the C₁₀ or C₁₂ carboxylate antimicrobial agent is selectedfrom the group consisting of: agents having the formula R—COOH whereinR═C₉ or C₁₁ n-alkyl, pharmaceutically acceptable salts thereof andcombinations thereof.
 23. The method of claim 19, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is selected from the group consisting ofn-capric acid, n-lauric acid, pharmaceutically acceptable salts thereofand combinations thereof.
 24. The method of claim 19, wherein thechelating agent is present in an amount ranging from about 0.1 mg/mL toabout 1 mg/mL and is selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 25.The method of claim 19, wherein the chelating agent is present in anamount ranging from about 0.25 mg/mL to about 0.5 mg/mL and is selectedfrom the group consisting of ethylenediaminetetraacetic acid,diethylenetriamine pentaacetic acid, ethylene glycol tetraacetic acid,etidronate, dimercaptosuccinic acid, deferoxamine, dimercaprol,triethylene tetramine dihydrochloride, zinc citrate, combination ofbismuth and citrate, penicillamine, pharmaceutically acceptable saltsthereof and combinations thereof.
 26. The method of claim 19, whereinthe microbial growth inhibiting solution further comprises a bufferpresent in an amount ranging from about 1.5 to about 24 mM, wherein theC₁₀ or C₁₂ carboxylate antimicrobial agent is present in an amountranging from about 0.071 mg/mL to about 1.15 mg/mL, and the chelatingagent is present in an amount ranging from about 0.0625 mg/mL to about 1mg/mL.
 27. The method of claim 26, wherein the C₁₀ or C₁₂ carboxylateantimicrobial agent comprises sodium caprate or socium laurate, thebuffer comprises citrate, and the chelating agent comprises disodiumethylenediaminetetraacetic acid.
 28. A medical device coated with amicrobial growth inhibiting solution comprising a C₁₀ or C₁₂ carboxylateantimicrobial agent and a chelating agent, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is present in an amount ranging fromabout 0.05 mg/mL to about 5 mg/mL and the chelating agent is present inan amount ranging from about 0.01 mg/mL to about 2 mg/mL, and whereinthe solution has a pH of 5.2 or less.
 29. The medical device of claim28, wherein the medical device is selected from the group of devicesconsisting of a central venous catheter, a peripheral intravenouscatheter, an arterial catheter, a Swant-Ganz catheter, a hemodialysiscatheter, an umbilical catheter, a percutaneous nontunneled siliconecatheter, a cuffed tunneled central venous catheter and a subcutaneouscentral venous pert.
 30. The medical device of claim 28, wherein the C₁₀or C₁₂ carboxylate antimicrobial agent is selected from the groupconsisting of: agents having the formula R—COOH wherein R═C₉ or C₁₁n-alkyl, pharmaceutically acceptable salts thereof and combinationsthereof.
 31. The medical device of claim 28, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is selected from the group consisting ofn-capric acid, n-lauric acid, pharmaceutically acceptable salts thereofand combinations thereof.
 32. The medical device of claim 28, whereinthe chelating agent is present in an amount ranging from about 0.1 mg/mLto about 1 mg/mL and is selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 33.The medical device of claim 28, wherein the chelating agent is presentin an amount ranging from about 0.25 mg/mL to about 0.5 mg/mL and isselected from the group consisting of ethylenediaminetetraacetic acid,diethylenetriamine pentaacetic acid, ethylene glycol tetraacetic acid,etidronate, dimercaptosuccinic acid, deferoxamine, dimercaprol,triethylene tetramine dihydrochloride, zinc citrate, combination ofbismuth and citrate, penicillamine, pharmaceutically acceptable saltsthereof and combinations thereof.
 34. The medical device of claim 28,wherein the microbial growth inhibiting solution further comprises abuffer present in an amount ranging from about 1.5 to about 24 mM,wherein the C₁₀ or C₁₂ carboxylate antimicrobial agent is present in anamount ranging from about 0.071 mg/mL to about 1.15 mg/mL, and thechelating agent is present in an amount ranging from about 0.0625 mg/mLto about 1 mg/mL.
 35. The medical device of claim 34, wherein the C₁₀ orC₁₂ carboxylate antimicrobial agent comprises sodium caprate or sociumlaurate, the buffer comprises citrate, and the chelating agent comprisesdisodium ethylenediaminetetraacetic acid.
 36. A method for lockingand/or flushing an implanted catheter, the method comprising: filling alumen of an implanted catheter open to a body lumen with a microbialgrowth inhibiting solution comprising a C₁₀ or C₁₂ carboxylateantimicrobial agent and a chelating agent, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is present in an amount ranging fromabout 0.05 mg/mL to about 5 mg/mL and the chelating agent is present inan amount ranging from about 0.01 mg/mL to about 2 mg/mL, and whereinthe solution has a pH of 5.2 or less.
 37. The method of claim 36,wherein the C₁₀ or C₁₂ carboxylate antimicrobial agent is selected fromthe group consisting of: agents having the formula R—COOH wherein R═C₉or C₁₁ n-alkyl, pharmaceutically acceptable salts thereof andcombinations thereof.
 38. The method of claim 36, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is selected from the group consisting ofn-capric acid, n-lauric acid, pharmaceutically acceptable salts thereofand combinations thereof.
 39. The method of claim 36, wherein thechelating agent is present in an amount ranging from about 0.1 mg/mL toabout 1 mg/mL and is selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 40.The method of claim 36, wherein the chelating agent is present in anamount ranging from about 0.25 mg/mL to about 0.5 mg/mL and is selectedfrom the group consisting of ethylenediaminetetraacetic acid,diethylenetriamine pentaacetic acid, ethylene glycol tetraacetic acid,etidronate, dimercaptosuccinic acid, deferoxamine, dimercaprol,triethylene tetramine dihydrochloride, zinc citrate, combination ofbismuth and citrate, penicillamine, pharmaceutically acceptable saltsthereof and combinations thereof.
 41. The method of claim 36, whereinthe microbial growth inhibiting solution further comprises a bufferpresent in an amount ranging from about 1.5 to about 24 mM, wherein theC₁₀ or C₁₂ carboxylate antimicrobial agent is present in an amountranging from about 0.071 mg/mL to about 1.15 mg/mL, and the chelatingagent is present in an amount ranging from about 0.0625 mg/mL to about 1mg/mL.
 42. The method of claim 41, wherein the C₁₀ or C₁₂ carboxylateantimicrobial agent comprises sodium caprate or socium laurate, thebuffer comprises citrate, and the chelating agent comprises disodiumethylenediaminetetraacetic acid.
 43. A kit for locking and/or flushingan implanted catheter, the kit comprising: a container holding a volumeof a microbial growth inhibiting solution comprising a C₁₀ or C₁₂carboxylate antimicrobial agent and a chelating agent, wherein the C₁₀or C₁₂ carboxylate antimicrobial agent is present in an amount rangingfrom about 0.05 mg/mL to about 5 mg/mL and the chelating agent ispresent in an amount ranging from about 0.01 mg/mL to about 2 mg/m, andwherein the solution has a pH of 5.2 or less L; and an implantablecatheter lumen that receives the microbial growth inhibiting solution.44. The kit of claim 43, wherein the container comprises a syringe. 45.The kit of claim 46, wherein the C₁₀ or C₁₂ carboxylate antimicrobialagent is selected from the group consisting of: agents having theformula R—COOH wherein R═C₉ or C₁₁ n-alkyl, pharmaceutically acceptablesalts thereof and combinations thereof.
 46. The kit of claim 43, whereinthe C₁₀ or C₁₂ carboxylate antimicrobial agent is selected from thegroup consisting of n-capric acid, n-lauric acid, pharmaceuticallyacceptable salts thereof and combinations thereof.
 47. The kit of claim43, wherein the chelating agent is present in an amount ranging fromabout 0.1 mg/mL to about 1 mg/mL and is selected from the groupconsisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylene glycol tetraacetic acid, etidronate,dimercaptosuccinic acid, deferoxamine, dimercaprol, triethylenetetramine dihydrochloride, zinc citrate, combination of bismuth andcitrate, penicillamine, pharmaceutically acceptable salts thereof andcombinations thereof.
 48. The kit of claim 43, wherein the chelatingagent is present in an amount ranging from about 0.25 mg/mL to about 0.5mg/mL and is selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 49.The kit of claim 43, wherein the microbial growth inhibiting solutionfurther comprises a buffer present in an amount ranging from about 1.5to about 24 mM, wherein the C₁₀ or C₁₂ carboxylate antimicrobial agentis present in an amount ranging from about 0.5 mM to about 8 mM, and thechelating agent is present in an amount ranging from about 0.0625 mg/mLto about 1 mg/mL.
 50. The kit of claim 49, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent comprises sodium caprate or sociumlaurate, the buffer comprises citrate, and the chelating agent comprisesdisodium ethylenediaminetetraacetic acid.
 51. A kit for locking and/orflushing an implanted catheter, the kit comprising: a container having afirst compartment holding a C₁₀ or C₁₂ carboxylate antimicrobial agentand a chelating agent in powder form and a second compartment holding apharmacologically acceptable carrier solution, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is present in an amount ranging fromabout 0.05 mg/mL to about 5 mg/mL and the chelating agent is present inan amount ranging from about 0.01 mg/mL to about 2 mg/mL when mixed withthe pharmacologically acceptable carrier solution, and wherein thesolution has a pH of 5.2 or less.
 52. The kit of claim 51, wherein thecontainer comprises an implantable catheter lumen or a syringe.
 53. Thekit of claim 51, wherein the C₁₀ or C₁₂ carboxylate antimicrobial agentis selected from the group consisting of: agents having the formulaR—COOH wherein R═C₉ or C₁₁ n-alkyl, pharmaceutically acceptable saltsthereof and combinations thereof.
 54. The kit of claim 51, wherein theC₁₀ or C₁₂ carboxylate antimicrobial agent is selected from the groupconsisting of n-capric acid, n-lauric acid, pharmaceutically acceptablesalts thereof and combinations thereof.
 55. The kit of claim 51, whereinthe chelating agent is present in an amount ranging from about 0.1 mg/mLto about 1 mg/mL when mixed with the pharmacologically acceptablecarrier solution and is selected from the group consisting ofethylenediaminetetraacetic acid, diethylenetriamine pentaacetic acid,ethylene glycol tetraacetic acid, etidronate, dimercaptosuccinic acid,deferoxamine, dimercaprol, triethylene tetramine dihydrochloride, zinccitrate, combination of bismuth and citrate, penicillamine,pharmaceutically acceptable salts thereof and combinations thereof. 56.The kit of claim 51, wherein the chelating agent is present in an amountranging from about 0.25 mg/mL to about 0.5 mg/mL when mixed with thepharmacologically acceptable carrier solution and is selected from thegroup consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, ethylene glycol tetraacetic acid, etidronate,dimercaptosuccinic acid, deferoxamine, dimercaprol, triethylenetetramine dihydrochloride, zinc citrate, combination of bismuth andcitrate, penicillamine, pharmaceutically acceptable salts thereof andcombinations thereof.
 57. The kit of claim 51, wherein first compartmentor the second compartment further comprises a buffer present in anamount ranging from about 1.5 to about 24 mM, wherein the C₁₀ or C₁₂carboxylate antimicrobial agent is present in an amount ranging fromabout 0.071 mg/mL to about 1.15 mg/mL, and the chelating agent ispresent in an amount ranging from about 0.0625 mg/mL to about 1 mg/mLwhen mixed with the pharmacologically acceptable carrier solution. 58.The kit of claim 57, wherein the C₁₀ or C₁₂ carboxylate antimicrobialagent comprises sodium caprate or socium laurate, the buffer comprisescitrate, and the chelating agent comprises disodiumethylenediaminetetraacetic acid.